This invention relates generally to thermostats for engine cooling systems. More particularly, this invention relates to cartridge thermostats with a housing that forms part of the cooling system for an internal combustion engine.
Internal combustion engines have cooling systems to prevent the engine from overheating. FIG. 1 shows a typical cooling system from the prior art. As illustrated, a water pump in the front cover pumps coolant through passageways surrounding the cylinder sleeves in the engine. The coolant flows through the cylinder head before entering a by-pass passage for return to the water pump. At the cylinder sleeves, a portion of the coolant is diverted to pass through the oil cooler before returning to the water pump.
A thermostat is positioned in the coolant passageway at the entrance of the by-pass in the cylinder head. The thermostat opens and closes depending upon the coolant temperature. When the coolant temperature rises above a particular temperature, the thermostat closes the by-pass passage and opens the radiator passage to divert coolant to the radiator. The coolant passes through the radiator before returning to the water pump.
In many internal combustion engines, the thermostat is positioned inside a thermostat housing. FIG. 2 shows this arrangement according to the prior art. A hose connects the thermostat housing to the radiator. The housing separates the radiator hose from the engine, thus making it easier to remove the radiator hose. While maintenance of the radiator and hoses is easier, the thermostat housing does not reduce the difficulties of replacing a thermostat.
To replace the thermostat, the housing must be removed. While it is routine to remove the bolts securing the housing to the engine, it is rather difficult to get to the housing. In many engines, the housing is located beneath or is obstructed by auxiliary equipment and other engine parts. These equipment and parts must be removed before there is sufficient access to remove the thermostat housing.
Moving the auxiliary equipment and engine parts increases the time and cost of replacing the thermostat. It also is a deterrent to replacing the thermostat as part of routine or preventative maintenance of the engine. This leads to overheating and breakdowns of the engine while it is in service.
Accordingly, there is a need for a thermostat which may be replaced with out removing the thermostat housing.
The present invention provides a cartridge thermostat system that permits removal and replacement of the thermostat without removing the housing or coolant manifold. In the cartridge thermostat system, a coolant manifold is mounted on a cylinder head of an engine. The cylinder head has an engine by-pass and a coolant port for receiving a pilot on the coolant manifold.
In a first embodiment, the coolant manifold has a thermostat port and a radiator passage. A cartridge thermostat screws into the thermostat port and operatively positions a plug adjacent to the engine by-pass. A wax plug in the cartridge thermostat expands when the coolant is hot to move the plug against the engine by-pass.
In a second embodiment, the cartridge thermostat operatively positions a plug adjacent to an engine by-pass and operatively positions a sleeve adjacent to a radiator passage. The plug and sleeve are connected to move together along a shaft on the cartridge thermostat. A wax plug expands when the coolant temperature increases, thus moving the plug and sleeve.
When the engine is cold the sleeve blocks the radiator passage. The engine by-pass is open permitting coolant to flow through the engine by-pass. When the engine is hot the wax plug moves the plug to close the engine by-pass. Coolant stops flowing through the engine by-pass. At the same time, the wax plug also moves the sleeve to open the radiator passage. Coolant flows through sleeve holes in the sleeve and through the radiator passage to the radiator.
In a third embodiment, the coolant manifold has a manifold by-pass and a radiator passage. The wax plug moves the sleeve to open and close the manifold by-pass and the radiator passage as the coolant temperature increases and decrease. The plug seals the engine by-pass.
In a fourth embodiment, the coolant manifold has two thermostat ports. This enables the same coolant manifold to be used on two engine configurations. The thermostat ports are connected by a coolant passage. The second thermostat port is connected independently to a manifold by-pass and a radiator passage.
In the first engine configuration, a cartridge plug extends through the first thermostat port. The cartridge plug seals the engine by-pass preventing coolant from flowing into the engine by-pass. A cartridge thermostat extends through the second thermostat port. The cartridge thermostat operatively positions a sleeve adjacent to the manifold by-pass and the radiator passage.
When the engine is cold, the sleeve blocks the radiator passage preventing coolant from circulating through the radiator. Coolant passes through the first thermostat port, through the coolant passage, through the second thermostat port, through sleeve holes in the sleeve, and through the manifold by-pass.
When the engine is hot, a wax plug in the cartridge thermostat expands and moves the sleeve to open the radiator passage and to block the manifold by-pass. Coolant passes through the first thermostat port, through the coolant passage, through the second thermostat port, and through the radiator passage to the radiator.
In the second engine configuration, a cartridge thermostat extends through the first thermostat port. The cartridge thermostat operatively positions a sleeve adjacent to the coolant passage. The cartridge thermostat also operatively positions the plug adjacent to the engine by-pass. The cartridge thermostat has a wax plug which expands when the coolant is hot. The wax plug moves the sleeve and plug together. A cartridge cap extends into the second thermostat port. The cartridge cap seals the second thermostat port. A manifold plug blocks the flow of coolant out of the manifold by-pass.
When the engine is cold, the sleeve blocks the coolant passage preventing coolant from circulating through the radiator. The plug is open permitting coolant to flow through the engine by-pass.
When the engine is hot, a wax plug in the cartridge thermostat expands and moves the sleeve to open the coolant passage. At the same time, the wax plug moves the plug to seal the engine by-pass. Coolant passes through the first thermostat port, through sleeve holes, through the coolant passage, through the second thermostat port, and through the radiator passage to the radiator.
As described, a wax plug is used to move the sleeve and/or plug in these embodiments. However, an electric or other operating means for a thermostat may be used to increase the stroke length of the thermostat. In addition, the diaphragm in the thermostat may be altered to also increase the stroke length. An optional air bleed system may be incorporated into the cap of the cartridge thermostat.
The following drawings and description set forth additional advantages and benefits of the invention. More advantages and benefits are obvious from the description and may be learned by practice of the invention.